1. Field of the Invention
The present invention relates to a display device that improves the reliability of connection in the case where an IC driver is connected by Chip On Glass (COG).
2. Description of the Related Art
A liquid crystal display device includes a thin film transistor (TFT) substrate on which pixel electrodes, TFTs, and the like are formed in a matrix arrangement and a counter substrate on which a black matrix, an overcoat film, or the like is formed at locations as matched with the pixel electrodes on the TFT substrate as the counter substrate is opposite to the TFT substrate, and liquid crystals are sandwiched between the TFT substrate and the counter substrate. Images are formed by controlling the optical transmittance of liquid crystal molecules for each pixel.
Since the liquid crystal display device is flat and light-weighted, the applications of the liquid crystal display device are widely spread in various fields from large-sized display devices such as a TV set to a mobile telephone, a DSC (Digital Still Camera), and the like. In order to externally supply electric power and signals to a liquid crystal display panel, a flexible wiring board is connected to a terminal unit on the TFT substrate. Moreover, in a small-sized liquid crystal display device, an IC driver is directly connected to a TFT substrate by COG. Also in the case where a flexible wiring board is connected to a TFT substrate as well as in the case where an IC driver is connected to a TFT substrate by COG, an anisotropic conductive film (ACF) is often used. The ACF includes conductive particles in a resin film, and the conductive particles conduct electricity between the terminal unit formed on the TFT substrate and the flexible wiring board, or between the terminal unit and the IC driver.
A terminal is formed in which a through hole is formed on a gate insulating film or a passivation film that is a protective film on a portion of a gate line or a drain line extending from a display region and the through hole is covered with a conductive metal oxide. Japanese Patent Application Laid-Open Publication No. 2000-221540 describes a configuration in which in the case where there are conductive beads between terminal through holes, a dummy through hole is formed between the terminals in order to prevent connections between conductive beads in the through holes and a flexible wiring board from being blocked by the conductive beads between the through holes. Namely, a dummy through hole is formed between terminals, so that such an event can be prevented by causing conductive beads to enter the dummy through hole that the electrical continuity of conductive beads on the terminals is blocked. Therefore, it is necessary to form the dummy through hole described in Japanese Patent Application Laid-Open Publication No. 2000-221540 on both sides of terminals.